Veterans’ Perceptions of Shared Autonomous Electric Shuttles: A Pre- and Post-Exposure Assessment

1. Summary

Thank you very much for taking the time to review this manuscript. Please find the detailed responses below and the corresponding revisions in track changes in the re-submitted files.

2. Point-by-point response to Comments and Suggestions for Authors

Comments 1: The overall structure of the article is not clear enough and easy to read. The manuscript already has 8 chapters. It is recommended to integrate chapters 5-8, which can help the article to be more logical, compact and better understood.

Response 1: Thank you for your suggestion. We have integrated chapters 5–8 as recommended to improve the clarity and flow of the manuscript. The changes can be found on Pages 18-20, Lines 619–748.

Comments 2: In lines 73-79 of chapter Introduction, the summary of existing studies is not detailed and rigorous enough. Some articles selected before are not strongly related to the topic of the article. The summary of literature needs to be discussed and analyzed in depth, and the significance and innovation of this research are pointed out.

Response 2: Thank you for your feedback. The discussion of the literature has been expanded to highlight the significance and innovation of this research. Further, we incorporated additional relevant studies that were not previously included. These changes can be found on Page 2, Lines 96–118.

Comments 3: For the method part, there is no description of the relevant theories and principles. Adding theoretical content helps to improve the scientific nature of the article, and this part also needs to be streamlined and integrated, and the expression of existing articles is not clear.

Response 2: Thank you for your feedback. We have revised the methodology section to include a discussion of the relevant theories. These changes can be found on Page 7, Lines 294–306.

1. Summary

Thank you very much for taking the time to review this manuscript. Please find the detailed responses below and the corresponding revisions in track changes in the re-submitted files.

2. Point-by-point response to Comments and Suggestions for Authors

Comments 1: Survey respondents were chosen from residents who “were able and willing to travel to one of the study locations”. Would this create biases in sample selection because it favors people who are willing to try out the new technology in the first place?

Response 1: Thank you for your feedback. The potential bias of selecting participants who are able and willing to travel to study locations is addressed in the limitations section of the manuscript. Specifically, it states (Page 18, Lines 768-771): “The quasi-experimental design and convenience sampling of the parent studies may have led to selection and spectrum bias, where participants with pre-existing positive views of AVs are overrepresented, that may have had the effect of potentially skewing the study's outcomes.”

Comments 2: Although the authors claim that the sample size is big enough, it still seems a bit small to reach statistically reliable results.

Response 2: Thank you for your feedback. The sample size was calculated using a priori power analysis in G*Power 3 software, with an alpha level of 0.05, a power of 0.80 for matched pairs with two measures (pre- and post-AS exposure), a medium effect size (Cohen’s d = 0.53), and a sample size of 30 participants was identified (See Page 5, Lines 240-248). The sample size was determined to be sufficient to detect statistically significant differences for the AVUPS-Total Acceptance (primary outcome variable), as stated in the manuscript (Page 9, Lines 419–420): “The current study is powered to assess the pre- and post-AS differences in AVUPS-Total Acceptance which is the primary outcome variable.” We also acknowledged the limitations of the sample size in detecting significant changes for other analyses, as noted in the manuscript (Page 19, Lines 976-978): “Although the study was adequately powered to detect differences in AVUPS-Total Acceptance, caution is warranted in interpreting the results of the secondary analyses due to the lack of specific power for these analyses.”

Comments 3: Questions included in AVUPS are heavily focusing on the perception of and less on experiences with autonomous vehicles. This limits the findings to only impacts of the presence of AS and not the quality of AS service itself.

Response 3: Thank you for your feedback. We acknowledge that the AVUPS primarily focuses on perceptions of autonomous shuttles rather than lived experiences. As part of the second phase of the parent studies, qualitative data was collected to assess participants' lived experiences with the autonomous shuttles. However, the results from this phase are beyond the scope of the current research article and will be published separately. We have modified the manuscript to explicitly indicate the above (Page 7, Lines 314-318).

Comments 4: Considering the data came from a parent study, it would be beneficial to compare the results of veterans with non-veterans.

Response 4: Thank you for your thoughtful suggestion. While a formal analysis comparing and contrasting Veterans and non-Veterans data was not conducted, a descriptive comparison has been added to the discussion section of the manuscript to provide additional context and insights (Page 17, Lines 698-715).

1. Summary

Thank you very much for taking the time to review this manuscript. Please find the detailed responses below and the corresponding revisions in track changes in the re-submitted files.

2. Point-by-point response to Comments and Suggestions for Authors

Comments 1: Although the objective of the paper is to investigate the perceptions of veterans on autonomous vehicles (AVs). A wider background related to the perceptions of AVs may be helpful.

Response 1: We appreciate the suggestion and in response, we have expanded the introduction to provide additional context on general perceptions of AVs (Page 2, Lines 96–118).

Comments 2: Many studies have investigated the perceptions of vulnerable road users, such as pedestrians, bicyclists, and disabilities, on AVs. Do the veterans belong to vulnerable road users? If so, a brief introduction about the perceptions of vulnerable road users on AVs is helpful. Please refer to  Das et al. (2021), and Ying et al. (2022),

References:

Das, S., 2021. Autonomous vehicle safety: understanding perceptions of pedestrians and bicyclists. Transp. Res. F: Traffic Psychol. Behav. 81, 41–54.

Xing, Y., Zhou, H., Han, X., Zhang, M., & Lu, J. (2022). What influences vulnerable road users’ perceptions of autonomous vehicles? A comparative analysis of the 2017 and 2019 Pittsburgh surveys. Technological Forecasting and Social Change, 176, 121454.

Response 2: Thank you for your comment. Veterans are not categorized as vulnerable road users in this study. While the two recommended studies were not included in the manuscript, the literature review in the introduction has been expanded to incorporate additional relevant studies (See Page 2, Lines 96–118).

1. Summary

Thank you very much for taking the time to review this manuscript. Please find the detailed responses below and the corresponding revisions in track changes in the re-submitted files.

2. Point-by-point response to Comments and Suggestions for Authors

Comments 1: This article, I suggest adding a section that lists and explains the features of these vehicles. It is also important to provide a broader context regarding the profiles of veteran users, particularly their familiarity with technology. While the article already includes demographic classifications, expanding on these to incorporate more insights into their contact with technology could enhance the discussion. Additionally, the study could benefit from a questionnaire exploring their thoughts on what autonomous vehicles and AI concepts entail, for example.

Response 1: Thank you for your suggestions. In response, additional information has been added to the manuscript to further explain the features of the autonomous shuttles utilized in the parent studies (Pages 3-4, Lines 173–218). While the Technology Readiness 2.0 questionnaire could provide a broader context regarding Veterans' familiarity with technology, this request falls outside the scope of this paper. We have however included this recommendation as a suggestion for future directions (Page 20, Lines 1049-1056). Similarly, while we agree that the study could benefit from a questionnaire exploring participants' thoughts on autonomous vehicles and AI concepts, this information was not collected as part of the parent studies and has also been added as future directions (Page 20, Lines 1049-1056).

Comments 2: Lastly, summarizing the findings and outlining the next steps for this research would add significant value to the work.

Response 2: Agree. We have, accordingly, added a summary of the findings to the discussion section of the manuscript (Page 17, Lines 716-727). Additionally, we have outlined the next steps for this research (i.e., future directions) to highlight areas for further exploration (Page 20, Lines 1049-1056).

1. Summary

Thank you very much for taking the time to review this manuscript. Please find the detailed responses below and the corresponding revisions in track changes in the re-submitted files.

2. Point-by-point response to Comments and Suggestions for Authors

Comments 1: The driving routes should be described in more detail, taking into account the prevailing traffic volumes (indicate similarities and differences).

Response 1: Thank you for your feedback. Additional details on the driving routes, including prevailing traffic volumes and their similarities and differences, have been added to the manuscript (Pages 5-7, Lines 266–293).

Comments 2: A graphical representation of the autonomous vehicle, the route traveled and the results would make the manuscript easier to understand.

Response 2: Thank you for the suggestion. Graphical representations of the autonomous shuttles (Page 4, Figure 1-2) and routes traveled have been added (Pages 6-7, Figure 3-6).

Comments 3: The study conducted contains limitations of “imperfections”, which the authors pointed out in Part Five. In this regard, I ask the authors to answer a few questions. Were the autonomous vehicles used in the experiment identical? If not, please describe them. 

What effect does the duration of one ride have on the results?

What is the effect on the results of the number of rides (trips) that one veteran took?

What effect does the behavior of other road users have on the results?

Response 3: Thank you for your feedback. Additional details have been provided to compare and contrast the two autonomous shuttles used in the parent studies (Page 3-4, Lines 173-214). While this research did not specifically analyze the effects of ride duration, the number of trips (all veterans in this study were exposed only once, but prior exposure was not accounted for), or the behavior of other road users, these have been added as suggestions for future research (Page 20, Lines 1049–1056).

Comments 4: Please compare the results obtained with those presented in other such works.

Response 4: Thank you for your feedback. The discussion section has been expanded to compare this study's results with similar works (Page 17, Lines 698–715).

Comments 5: Why in Table 1 “Rural = 7; Urban = 31” when “The Villages n=39”?               

Response 5: Thank you for your observation. The discrepancy arises due to missing data for one participant who did not provide information regarding their residential location (rural or urban). We have added this information to the Note section of the Table to indicate this information (Page 11, Line 484).

Comments 6: Why does Table No. 3 show results for n=63 urban veterans and n=13 rural veterans when all veterans were n=77?

Response 6: Thank you for your observation. Similarly, this discrepancy is due to missing data from one Veteran who did not provide information regarding their residential location (rural or urban). We have updated the Note section of the table to reflect this information (Page 12, Lines 528-529).